Modifiers

Modifiers

Modifiers - refine billing with CPT/HCPCS qualifiers

Modifiers add detail to billed CPT/HCPCS codes so payers understand how, where, or why a test was performed. Used correctly, they reduce denials by clarifying medical necessity and circumstances.

Common laboratory modifiers

  • 90 — Reference (outside) laboratory: use when testing was performed by a send‑out lab.
  • 91 — Repeat clinical diagnostic laboratory test: medically necessary repeat of the same test on the same day; not for QC repeats or instrument reruns.
  • QW — CLIA‑waived test: required for many waived assays.
  • 59 (and Medicare’s subsets XE/XS/XP/XU) — Distinct procedural service: separate specimen, encounter, or anatomical site when unbundling is appropriate.
  • 92 — Alternative laboratory platform testing: point‑of‑care/portable platforms (use only when payer policy applies).

Best practices

  • Follow payer policies (LCDs/NCDs) and clearinghouse edits—usage varies by payer.
  • Document the rationale in the order/case notes (e.g., “Repeat due to new specimen at 14:00”).
  • Do not use 91 for instrument reruns, failed QC, or reflex algorithms unless policy allows.
  • Apply QW only to CLIA‑waived tests listed as such; keep CLIA certificates current.
  • For 59 (or XE/XS/XP/XU), ensure clear documentation of distinct specimens/times/sites.
  • Build LIS rules to auto‑suggest modifiers based on test attributes (waived, send‑out, repeat within timeframe), but require user confirmation for edge cases.
  • Audit regularly: monitor denials tied to modifier misuse and adjust rules/mappings.

Getting started in the LIS

  • Maintain a central modifier list with descriptions.
  • Map allowed modifiers to specific CPTs/tests.
Info

Note: If you plan to perform billing in‑house, the OCL LIS support team can upload a complete library of modifiers.



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